Remember that you have to make one post either a question or an answer to a questions. Please keep comments physics related...I will be reading these. Fell free to answer mulitple times.
A famous jockey dies and leaves his will behind to decide how his fortune will be divided among his two sons. The will states that his two sons will have a horse race, and whoever's horse finishes second will be the inheriter of the fortune. Inevitably, on the day of the race after the gun had sounded both of the brothers just stood around waiting for the other to finsih. This dilemma persisited for quite sometime, until an arbitrator stepped in. Without dishonoring any parts of the will,the arbitrator made one small tweak and when the race was held again the two brothers actually raced to the finish line. What change did the arbitrator make? (Remember he didn't change any parts of the will)
Moez, I thought that acceleration was always -9.8m/s^2 either when thrown up or when falling back down. Because gravity is always acting upon the object. Remember, God doesn't just turn gravity on and off like Rodino said with a huge switch.
The "magnitude" of acceleration is always a positive number though, im pretty sure.
The aforementioned also kinda goes with my question on the Multiple Choice question 5. I think that the wording is confusing because when it says "while its acceleration is decreasing" they dont specify the magnitude or if the acceleration is just negative. What do you think?
@ Jeff: hey jeff, my dad just helped me with that problem, magnitude and "-" don't matter.
The Answer is Yes BECAUSE, think of it this way.
Your in a car at rest, and you SLAM THE PETAL right? Now your car is starting at its maximum acceleration, as the car continues to go faster, you'll relax your foot off the petal, and your acceleration if now decreasing. Yet, as you got faster, you let the gas petal go a little by little. So, as you got faster, your acceleration was decreasing.
It made sense to me :P
So if you START at maximum acceleration, and then let off the pedal as you accelerate, your acceleration is going down, yet your speed is going up. Its not "instant" change, so that's why its air friction one. Because like the air behind you would push you for a bit even if your acceleration was like really low, so you WOULD speed up for like .5 mph while acceleration was going down.
if you consider "going upwards" to always be positive and you consider "going downwards" to always be negative then yeah basically it will be -9.8 since you consider downwards to be negative
i'm confused now after reading all these comments on gravity. so basically from the comments... 1. acceleration of gravity when throwing something up = -9.8m/s2 2. acceleration of gravity when object that was thrown up is coming down = -9.8m/s2 3. acceleration of gravity when throwing an object down = 9.8m/s2 yes? or no? i don't understand the last one.. i thought accleration of gravity is always -9.8m/s2
i have the ti-84 and when i convert a number and i get like... 2.2 repeating then.. how do i copy/trace that to use that EXACT number in my calculations?
The arbitrator told them to switch horses because whichever horse finishes second wins not whichever person. So the first one to finish would get the fortune.
How do you know which equation to use? I will use one and get a different answer for the same variable when I use another. and sometimes I can't help but use a variable I just solved for.
I was just wondering if there were obvious signs to know whether or not some of the unknowns can be figured out from the given information before we use our three formulas ????????
@Frances - For your #3 that is only considering down as a positive i.e. You want to go left instead of right, so left is positive and right is negative, except in this case down is positive and up is negative. But you can completely disregard that and just make down always negative in which case gravity is ALWAYS -9.8 m/s^2
ok so im not sure if this is the right way to do number 15 but the way i found it was by using the third equation because you dont know the initial velocity but you do know that its acceleration is allways -9.8m/s^2 because of gravity and so it will reach its peak where the velcosity is zero at 5 seconds because it comes back down at the same speed so its at the halfway. so basically my equation was:
i thought acceleration was always-9.8. how could it be positive? its acceleration due to gravity so isnt it always supposed 2 be negative because gravity is acting downwards?
kmukhi_93 Which graphing calculator are you using?? if you have 84, you go to MATH -> find SOLVER -> type in your equation -> press enter. then you'll see x=0,so you type in 10 instead of 0 and press ALPHA and enter. then you'll get your answer! i hope it's not too cofusing
if you have t89 then you go to home and hit f2 click solve( then you type in your equation solve(x^2 + x = 0 , x) then hit enter always do "," then the variable you are using at the end to define what solver is solving for
Kirtan If you're using an 89 and haven't figured it out, press f2 for algebra, select solve, then type in the equation and enter the variable at the end. solve(equation,x) If there's two equations: solve(equation1 and equation2,{x,y}) "and" can be found in the catalog.
okay so i'm kinda confused with all this pos/neg 9.8 talk as well. but from what i got...it's always negative. i don't think it should be made more confusing than it is.
Ryan: for the multiple choice #2, it's basically the same as problem #3 on the practice problems 1 worksheet. you find runner B (the slower runner's) average velocity (avg. v=d/t) then multiply the slower runner's velocity by the faster runner's time. so you get the distance of where the slower runner would be when the faster one crossed the finish line, and then subtract by 100m. i hope that makes sense...it's really hard to explain stuff using a computer...
A famous jockey dies and leaves his will behind to decide how his fortune will be divided among his two sons. The will states that his two sons will have a horse race, and whoever's horse finishes second will be the inheriter of the fortune. Inevitably, on the day of the race after the gun had sounded both of the brothers just stood around waiting for the other to finsih. This dilemma persisited for quite sometime, until an arbitrator stepped in. Without dishonoring any parts of the will,the arbitrator made one small tweak and when the race was held again the two brothers actually raced to the finish line. What change did the arbitrator make? (Remember he didn't change any parts of the will)
ReplyDeleteif an object is thrown up, the acceleration is -9.8 but when it comes back down is acceleration 9.8 or just -9.8?
ReplyDeleteacceleration would be 9.8 because the object is going the same direction as gravity (which is downwards)
ReplyDeleteMoez, I thought that acceleration was always
ReplyDelete-9.8m/s^2 either when thrown up or when falling back down. Because gravity is always acting upon the object. Remember, God doesn't just turn gravity on and off like Rodino said with a huge switch.
The "magnitude" of acceleration is always a positive number though, im pretty sure.
The aforementioned also kinda goes with my question on the Multiple Choice question 5. I think that the wording is confusing because when it says "while its acceleration is decreasing" they dont specify the magnitude or if the acceleration is just negative. What do you think?
hi this is JAMIE YANG NOT james lee, my gmail account just says im james
ReplyDeletethe acceleration would be -9.8 because like moez said, it would be going the same direction as gravity, which is downwards, which is negative...
also gravity always acts on objects with an acceleration of -9.8, and it wouldnt suddenly change if you threw the object or not...
i dont understand number 14. which equation do we use to answer it??
sorry i made a typo i meant to have -9.8 because downwards is negative
ReplyDeleteJeff, for #5, i think its just negative, otherwise it's not possible?
ReplyDeletehey jamie
ReplyDeletefor 14 use the second equation except rearrange it to solve for d so it looks like:
d=(v^2 - v0^2)/2a
we know for both balls the final velocity is 0 and the acceleration is -9.8 m/s^2 thus when you compare the ratio of the distances you get
d2/d1 = -(2v)^2 / -(v)^2 which makes the ratio 4:1
@ Jeff: hey jeff, my dad just helped me with that problem, magnitude and "-" don't matter.
ReplyDeleteThe Answer is Yes BECAUSE, think of it this way.
Your in a car at rest, and you SLAM THE PETAL right? Now your car is starting at its maximum acceleration, as the car continues to go faster, you'll relax your foot off the petal, and your acceleration if now decreasing. Yet, as you got faster, you let the gas petal go a little by little. So, as you got faster, your acceleration was decreasing.
It made sense to me :P
So if you START at maximum acceleration, and then let off the pedal as you accelerate, your acceleration is going down, yet your speed is going up. Its not "instant" change, so that's why its air friction one. Because like the air behind you would push you for a bit even if your acceleration was like really low, so you WOULD speed up for like .5 mph while acceleration was going down.
Get it?
How do you set up an equation for problem #2 on the Practice Multiple Choice?
ReplyDelete-Ryan Yang
uhhhhhh, im confused about what everyone said,,,, so it's ALWAYS -9.8????
ReplyDeleteALWAYS??? no matter what?
well think of it this way:
ReplyDeleteif you consider "going upwards" to always be positive and you consider "going downwards" to always be negative then yeah basically it will be -9.8 since you consider downwards to be negative
however if say you send an object downward then its acceleration will be 9.8 since they are going the same negative direction
ReplyDeletedo you get that?
i'm confused now after reading all these comments on gravity.
ReplyDeleteso basically from the comments...
1. acceleration of gravity when throwing something up = -9.8m/s2
2. acceleration of gravity when object that was thrown up is coming down = -9.8m/s2
3. acceleration of gravity when throwing an object down = 9.8m/s2
yes? or no? i don't understand the last one.. i thought accleration of gravity is always -9.8m/s2
i have the ti-84 and when i convert a number and i get like... 2.2 repeating then.. how do i copy/trace that to use that EXACT number in my calculations?
This comment has been removed by the author.
ReplyDeleteTo Moez
ReplyDeleteThe arbitrator told them to switch horses because whichever horse finishes second wins not whichever person. So the first one to finish would get the fortune.
does that count as one post?
ReplyDeleteWell i have a question anyway,
How do you know which equation to use? I will use one and get a different answer for the same variable when I use another. and sometimes I can't help but use a variable I just solved for.
This is James Lee, for number 15 on the MC, how would you even start the problem? All they give you is that the bullet was in the air for 10 seconds?
ReplyDeleteCan anyone remind me how to use solver
ReplyDelete?
Mr. Rodino, this is kirtan patel, my username is my indian name.
james idk either
ReplyDeleteI was just wondering if there were obvious signs to know whether or not some of the unknowns can be figured out from the given information before we use our three formulas
ReplyDelete????????
@Frances - For your #3 that is only considering down as a positive i.e. You want to go left instead of right, so left is positive and right is negative, except in this case down is positive and up is negative. But you can completely disregard that and just make down always negative in which case gravity is ALWAYS -9.8 m/s^2
ReplyDeleteok so im not sure if this is the right way to do number 15 but the way i found it was by using the third equation because you dont know the initial velocity but you do know that its acceleration is allways -9.8m/s^2 because of gravity and so it will reach its peak where the velcosity is zero at 5 seconds because it comes back down at the same speed so its at the halfway. so basically my equation was:
ReplyDelete(0m/s)=Vnot + (-9.8m/s^2)(5s) it comes to 49m/s
please let me know if i did that correct
i thought acceleration was always-9.8. how could it be positive? its acceleration due to gravity so isnt it always supposed 2 be negative because gravity is acting downwards?
ReplyDeleteHi this is Risa
ReplyDeletekmukhi_93
Which graphing calculator are you using??
if you have 84, you go to MATH -> find SOLVER ->
type in your equation -> press enter.
then you'll see x=0,so you type in 10 instead of 0 and press ALPHA and enter. then you'll get your answer!
i hope it's not too cofusing
Kirtan
ReplyDeleteif you have t89 then you go to home and hit f2
click solve(
then you type in your equation
solve(x^2 + x = 0 , x) then hit enter always do "," then the variable you are using at the end to define what solver is solving for
Kirtan
ReplyDeleteIf you're using an 89 and haven't figured it out, press f2 for algebra, select solve, then type in the equation and enter the variable at the end.
solve(equation,x)
If there's two equations:
solve(equation1 and equation2,{x,y})
"and" can be found in the catalog.
okay so i'm kinda confused with all this pos/neg 9.8 talk as well.
ReplyDeletebut from what i got...it's always negative. i don't think it should be made more confusing than it is.
Ryan: for the multiple choice #2, it's basically the same as problem #3 on the practice problems 1 worksheet.
you find runner B (the slower runner's) average velocity
(avg. v=d/t)
then multiply the slower runner's velocity by the faster runner's time.
so you get the distance of where the slower runner would be when the faster one crossed the finish line, and then subtract by 100m.
i hope that makes sense...it's really hard to explain stuff using a computer...
wow i was going to ask a question about the gravity and stuff but it was so efficiently explained by my superior class mates. Thanks guys
ReplyDelete